软土地区恒载作用下单桩和群桩的抗拔试验分析

Field Tests on Uplift Behavior of Bored Cast-in-place Single or Group Piles Under Constant Load in Soft Ground

根据上海某工程单桩、群桩的静载抗拔试验结果,分析了上海软土地区扩底和等截面钻孔灌注桩在恒载作用下的抗拔稳定性。软土地区扩底钻孔灌注桩的单桩、群桩和等截面钻孔灌注桩的终极维持荷载法试验结果表明,在维持荷载过程中桩顶位移变化随时间的推移越来越小,维持30h^50h后基本趋于稳定状态;试验结果也表明当扩底钻孔灌注桩群桩的中心间距大于3倍的扩底直径时,群桩效应不明显。该试验成果为上海软土地区的桩基工程设计和施工提供了有价值的参数。

On the basis of single instrumented pile and group instrumented piles ＇ static uplift load test result, the stability of enlarge bottom or uniform section bored piles in soft ground in Shanghai is analysed. The test result indicates that the diaplacement of single instrumented pile or group instrumented piles and uniform section pile was very little throughout the constant load, and the rate of displacement diminished distinctly at the end of the test. It states that the variation of pile top displacement decrease with time and becomes stable after 30h -50h. The test result indicates that the domino effect of pile group with enlarged bottom is not obvious when the spacing in piles center is longer than triplicate diameter of enlarged bottom. The parameter was provided as valuable reference to pile designing and construction in soft ground in Shanghai.